YB1685 2A 380KHz 32V PWM Buck DC/DC Converter Description Features The YB1685 is a 380 KHz fixed frequency monolithic step down switch mode regulator with a built in internal Power MOSFET. It achieves 2A continuous output current over a wide input supply range with excellent load and line regulation. The device includes a voltage reference, oscillation circuit, error amplifier, internal PMOS and etc. 2A Constant Output Current The PWM control circuit is able to adjust the duty ratio linearly from 0 to 100%. An enable function, an over current protection function and a short circuit protection function are built inside. An internal compensation block is built in to minimize external component count. The YB1685 serves as ideal power supply units for portable devices. LCD Monitor / TV 140mΩ RDSON Internal Power PMOSFET Switch Up to 92% Efficiency Fixed 380KHz Frequency Wide 3.6V to 32V Input Voltage Range Output Adjustable from 1.235V to 30V Output Current Protection Built in Frequency Compensation Built in Thermal Shutdown Function Built in Current Limit Function SOP8 Package is Available The Minimum Dropout up to 0.3V Pb-free Package Applications Portable DVD Battery Charger ADSL Modem Telecom / Networking Equipment Typical Application Circuit Figure 1: Typical Application Circuit YB1685 Rev.1.0 www.yobon.com.tw 1 YB1685 2A 380KHz 32V PWM Buck DC/DC Converter Pin Configuration NC 1 8 NC VIN 2 7 EN SW 3 6 NC GND 4 5 FB SOP-8 Figure 2: Pin Configuration Pin Description Table 1 Pin Name Description 1,6,8 NC Not Connect. 2 VIN Supply Voltage Input Pin. YB1685 operates from a 3.6V to 32VDC voltage. Bypass VIN to GND with a suitably large capacitor to eliminate noise on the input. 3 SW Power Switch Output Pin. SW is the switch node that supplies power to the output. Ground Pin. Care must be taken in layout. This pin should be placed outside of the Schottky Diode to output capacitor ground path to prevent switching current spikes from inducing voltage noise into YB1685. 4 GND 5 FB Feedback Pin. Through an external resistor divider network, FB senses the output voltage and regulates it. The feedback threshold voltage is 1.235V. 7 EN Enable Pin. EN is a digital input that turns the regulator on or off. Drive EN pin high to turn on the regulator, drive it low to turn it off. Ordering Information Order Number Package Type Supplied As Package Marking YB1685SPX8P SOP-8 2500 units Tape & Reel Please contact sales representative YB1685 Rev.1.0 www.yobon.com.tw 2 YB1685 2A 380KHz 32V PWM Buck DC/DC Converter Absolute Maximum Ratings Recommended Operating Conditions Input Voltage............................. -0.3V to 32V Feedback Pin Voltage .................-0.3V to VIN Enable Pin Voltage.................... -0.3V to 12V Switch Pin Voltage ......................-0.3V to VIN Power Dissipation .............. Internally Limited Operating Junction Temperature......... 150°C Storage Temperature ............ -65°C to 150°C Input Voltage............................ 3.6V to 32V Operating Junction Temperature ... -40°C to 125°C Operating Ambient Temperature.......-40°C to 85°C Lead Temperature (Soldering, 10 sec)... 260°C ESD (HBM).......................................2000V Note: Stresses greater than those listed under Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability. Electrical Characteristics Table 2 (VCC = 12V, TA=25°C, unless otherwise specified.) Description Input Voltage Shutdown Supply Current Symbol Test Conditions VIN ISTBY MIN TYP 3.6 MAX Units 32 V VEN = 0V 30 90 µA 3.6 4 mA 1.235 1.26 V 0.1 0.5 µA 3 4 A Supply Current ICC VEN = 2V, VFB = 1.3V Feedback Voltage VFB VIN = 3.6V to 23V Feedback Bias Current IFB VFB = 1.3V Switch Current Limit ILIM Oscillator Frequency FOSC 320 380 440 KHz EN Pin Threshold VEN 0.7 1.2 1.7 V 1.21 EN Pin Input Leakage Current IH VEN = 2.5V -0.1 -1 µA IL VEN = 0.5V -3 -10 µA Internal PMOS RDSON RDSON VIN ≦ 12V, VFB =0V VEN = 12V, IOUT = 2A 140 mΩ Max. Duty Cycle DMAX VFB = 0V, ISW = 0.1A 100 % VIN = 12V, VOUT = 5V, IOUT = 2A 92 % 165 °C Efficiency Thermal Shutdown YB1685 Rev.1.0 η TOTSD www.yobon.com.tw 3 YB1685 2A 380KHz 32V PWM Buck DC/DC Converter Typical Performance Characteristics Efficiency V.S Load (Vin=12V) System Efficiency(%) 100% 90% 80% 2.5V 70% 3.3V 60% 5V 50% 0 0.5 1 1.5 2 Output Load Current(A) YB1685 Rev.1.0 www.yobon.com.tw 4 YB1685 2A 380KHz 32V PWM Buck DC/DC Converter Function Block Figure 3: Function Block Functional Description VIN This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. Gnd Circuit ground. SW Internal switch. The voltage at this pin and switches between (VIN – VGS) approximately – 0.5V, with a duty cycle of approximately VOUT / VIN. To minimize coupling to sensitive circuitry, the PC board copper area connected to this pin should be kept a minimum. YB1685 Rev.1.0 FB Senses the regulated output voltage to complete the feedback loop. EN Allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 30µA. Pulling this pin below a threshold voltage of approximately 0.7V turns the regulator down, and pulling this pin above 1.3V (up to a maximum of 12V) shuts the regulator on. For automatic star up condition, can be implemented by the addition of a resistive voltage divider from VIN to GND. www.yobon.com.tw 5 YB1685 2A 380KHz 32V PWM Buck DC/DC Converter Thermal Considerations The SOP8 package needs a heat sink under most conditions. The size of the heat sink depends on the input voltage, the output voltage, the load current and the ambient temperature. The YB1685 junction temperature rises above ambient temperature for a 2A load and different input and output voltages. The data for these curves was taken with the YB1685 (SOP8 package) operating as a buck-switching regulator in an ambient temperature of 25 ºC (still air). These temperature rise numbers are all approximate and there are many factors that can affect these temperatures. Higher ambient temperatures require more heat sinking. copper Thick ness, single or double-sided, multi-layer board and the amount of solder on the board. The effectiveness of the PC board to dissipate heat also depends on the size, quantity and spacing of other components on the board, as well as whether the surrounding air is still or moving. Furthermore, some of these components such as the catch diode will add heat to the PC board and the heat can vary as the input voltage changes. For the inductor, depending on the physical size, type of core material and the DC resistance, it could either act as a heat sink taking heat away from the board, or it could add heat to the board. For the best thermal performance, wide copper traces and generous amounts of printed circuit board copper should be used in the board layout. (Once exception to this is the output (switch) pin, which should not have large areas of copper.) Large areas of copper provide the best transfer of heat (lower thermal resistance) to the surrounding air, and moving air lowers the thermal resistance even further. Package thermal resistance and junction temperature rise numbers are all approximate, and there are many factors that will affect these numbers. Some of these factors include board size, shape, thickness, position, location, and even board temperature. Other factors are, trace width, total printed circuit copper area, YB1685 Rev.1.0 www.yobon.com.tw 6 YB1685 2A 380KHz 32V PWM Buck DC/DC Converter Typical Application Circuit YB1685 Rev.1.0 www.yobon.com.tw 7 YB1685 2A 380KHz 32V PWM Buck DC/DC Converter Schottky Rectifier Selection Guide YB1685 Lists some rectifier manufacturers. VIN (Max) 20V 2A Load Current Part Number B220 Diodes, Inc. SK23 Pan Jit International SR22 Pan Jit International 20QB030 30V Vendor International Rectifier B230 Diodes, Inc. SK23 Pan Jit International SR23 General Semiconductor, Pan Jit International SS23 General Semiconductor Output Voltage vs. R1, R2 Resistor Selection Guide ( VOUT = ( 1 + R1 / R2 ) * 1.235V ) YB1685 VOUT vs. R1, R2 Select Table VOUT R1 R2 1.8V 5.1K 11K 2.5V 5.1K 5K 3.3V 2.7K 1.6K 5V 11K 3.6K 9V 43K 6.8K 12V 13K 1.5K YB1685 Rev.1.0 www.yobon.com.tw 8 YB1685 2A 380KHz 32V PWM Buck DC/DC Converter Package Information (SOP-8) NOTICE: y The information described herein is subject to change without notice. y Yobon does not assume any responsibility for use of any circuitry or applications described herein, nor does it convey any patent license. YB1685 Rev.1.0 www.yobon.com.tw 9